linux/fs/ecryptfs/read_write.c
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   1/**
   2 * eCryptfs: Linux filesystem encryption layer
   3 *
   4 * Copyright (C) 2007 International Business Machines Corp.
   5 *   Author(s): Michael A. Halcrow <mahalcro@us.ibm.com>
   6 *
   7 * This program is free software; you can redistribute it and/or
   8 * modify it under the terms of the GNU General Public License as
   9 * published by the Free Software Foundation; either version 2 of the
  10 * License, or (at your option) any later version.
  11 *
  12 * This program is distributed in the hope that it will be useful, but
  13 * WITHOUT ANY WARRANTY; without even the implied warranty of
  14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15 * General Public License for more details.
  16 *
  17 * You should have received a copy of the GNU General Public License
  18 * along with this program; if not, write to the Free Software
  19 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
  20 * 02111-1307, USA.
  21 */
  22
  23#include <linux/fs.h>
  24#include <linux/pagemap.h>
  25#include "ecryptfs_kernel.h"
  26
  27/**
  28 * ecryptfs_write_lower
  29 * @ecryptfs_inode: The eCryptfs inode
  30 * @data: Data to write
  31 * @offset: Byte offset in the lower file to which to write the data
  32 * @size: Number of bytes from @data to write at @offset in the lower
  33 *        file
  34 *
  35 * Write data to the lower file.
  36 *
  37 * Returns bytes written on success; less than zero on error
  38 */
  39int ecryptfs_write_lower(struct inode *ecryptfs_inode, char *data,
  40                         loff_t offset, size_t size)
  41{
  42        struct file *lower_file;
  43        mm_segment_t fs_save;
  44        ssize_t rc;
  45
  46        lower_file = ecryptfs_inode_to_private(ecryptfs_inode)->lower_file;
  47        if (!lower_file)
  48                return -EIO;
  49        fs_save = get_fs();
  50        set_fs(get_ds());
  51        rc = vfs_write(lower_file, data, size, &offset);
  52        set_fs(fs_save);
  53        mark_inode_dirty_sync(ecryptfs_inode);
  54        return rc;
  55}
  56
  57/**
  58 * ecryptfs_write_lower_page_segment
  59 * @ecryptfs_inode: The eCryptfs inode
  60 * @page_for_lower: The page containing the data to be written to the
  61 *                  lower file
  62 * @offset_in_page: The offset in the @page_for_lower from which to
  63 *                  start writing the data
  64 * @size: The amount of data from @page_for_lower to write to the
  65 *        lower file
  66 *
  67 * Determines the byte offset in the file for the given page and
  68 * offset within the page, maps the page, and makes the call to write
  69 * the contents of @page_for_lower to the lower inode.
  70 *
  71 * Returns zero on success; non-zero otherwise
  72 */
  73int ecryptfs_write_lower_page_segment(struct inode *ecryptfs_inode,
  74                                      struct page *page_for_lower,
  75                                      size_t offset_in_page, size_t size)
  76{
  77        char *virt;
  78        loff_t offset;
  79        int rc;
  80
  81        offset = ((((loff_t)page_for_lower->index) << PAGE_CACHE_SHIFT)
  82                  + offset_in_page);
  83        virt = kmap(page_for_lower);
  84        rc = ecryptfs_write_lower(ecryptfs_inode, virt, offset, size);
  85        if (rc > 0)
  86                rc = 0;
  87        kunmap(page_for_lower);
  88        return rc;
  89}
  90
  91/**
  92 * ecryptfs_write
  93 * @ecryptfs_inode: The eCryptfs file into which to write
  94 * @data: Virtual address where data to write is located
  95 * @offset: Offset in the eCryptfs file at which to begin writing the
  96 *          data from @data
  97 * @size: The number of bytes to write from @data
  98 *
  99 * Write an arbitrary amount of data to an arbitrary location in the
 100 * eCryptfs inode page cache. This is done on a page-by-page, and then
 101 * by an extent-by-extent, basis; individual extents are encrypted and
 102 * written to the lower page cache (via VFS writes). This function
 103 * takes care of all the address translation to locations in the lower
 104 * filesystem; it also handles truncate events, writing out zeros
 105 * where necessary.
 106 *
 107 * Returns zero on success; non-zero otherwise
 108 */
 109int ecryptfs_write(struct inode *ecryptfs_inode, char *data, loff_t offset,
 110                   size_t size)
 111{
 112        struct page *ecryptfs_page;
 113        struct ecryptfs_crypt_stat *crypt_stat;
 114        char *ecryptfs_page_virt;
 115        loff_t ecryptfs_file_size = i_size_read(ecryptfs_inode);
 116        loff_t data_offset = 0;
 117        loff_t pos;
 118        int rc = 0;
 119
 120        crypt_stat = &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
 121        /*
 122         * if we are writing beyond current size, then start pos
 123         * at the current size - we'll fill in zeros from there.
 124         */
 125        if (offset > ecryptfs_file_size)
 126                pos = ecryptfs_file_size;
 127        else
 128                pos = offset;
 129        while (pos < (offset + size)) {
 130                pgoff_t ecryptfs_page_idx = (pos >> PAGE_CACHE_SHIFT);
 131                size_t start_offset_in_page = (pos & ~PAGE_CACHE_MASK);
 132                size_t num_bytes = (PAGE_CACHE_SIZE - start_offset_in_page);
 133                loff_t total_remaining_bytes = ((offset + size) - pos);
 134
 135                if (fatal_signal_pending(current)) {
 136                        rc = -EINTR;
 137                        break;
 138                }
 139
 140                if (num_bytes > total_remaining_bytes)
 141                        num_bytes = total_remaining_bytes;
 142                if (pos < offset) {
 143                        /* remaining zeros to write, up to destination offset */
 144                        loff_t total_remaining_zeros = (offset - pos);
 145
 146                        if (num_bytes > total_remaining_zeros)
 147                                num_bytes = total_remaining_zeros;
 148                }
 149                ecryptfs_page = ecryptfs_get_locked_page(ecryptfs_inode,
 150                                                         ecryptfs_page_idx);
 151                if (IS_ERR(ecryptfs_page)) {
 152                        rc = PTR_ERR(ecryptfs_page);
 153                        printk(KERN_ERR "%s: Error getting page at "
 154                               "index [%ld] from eCryptfs inode "
 155                               "mapping; rc = [%d]\n", __func__,
 156                               ecryptfs_page_idx, rc);
 157                        goto out;
 158                }
 159                ecryptfs_page_virt = kmap_atomic(ecryptfs_page);
 160
 161                /*
 162                 * pos: where we're now writing, offset: where the request was
 163                 * If current pos is before request, we are filling zeros
 164                 * If we are at or beyond request, we are writing the *data*
 165                 * If we're in a fresh page beyond eof, zero it in either case
 166                 */
 167                if (pos < offset || !start_offset_in_page) {
 168                        /* We are extending past the previous end of the file.
 169                         * Fill in zero values to the end of the page */
 170                        memset(((char *)ecryptfs_page_virt
 171                                + start_offset_in_page), 0,
 172                                PAGE_CACHE_SIZE - start_offset_in_page);
 173                }
 174
 175                /* pos >= offset, we are now writing the data request */
 176                if (pos >= offset) {
 177                        memcpy(((char *)ecryptfs_page_virt
 178                                + start_offset_in_page),
 179                               (data + data_offset), num_bytes);
 180                        data_offset += num_bytes;
 181                }
 182                kunmap_atomic(ecryptfs_page_virt);
 183                flush_dcache_page(ecryptfs_page);
 184                SetPageUptodate(ecryptfs_page);
 185                unlock_page(ecryptfs_page);
 186                if (crypt_stat->flags & ECRYPTFS_ENCRYPTED)
 187                        rc = ecryptfs_encrypt_page(ecryptfs_page);
 188                else
 189                        rc = ecryptfs_write_lower_page_segment(ecryptfs_inode,
 190                                                ecryptfs_page,
 191                                                start_offset_in_page,
 192                                                data_offset);
 193                page_cache_release(ecryptfs_page);
 194                if (rc) {
 195                        printk(KERN_ERR "%s: Error encrypting "
 196                               "page; rc = [%d]\n", __func__, rc);
 197                        goto out;
 198                }
 199                pos += num_bytes;
 200        }
 201        if (pos > ecryptfs_file_size) {
 202                i_size_write(ecryptfs_inode, pos);
 203                if (crypt_stat->flags & ECRYPTFS_ENCRYPTED) {
 204                        int rc2;
 205
 206                        rc2 = ecryptfs_write_inode_size_to_metadata(
 207                                                                ecryptfs_inode);
 208                        if (rc2) {
 209                                printk(KERN_ERR "Problem with "
 210                                       "ecryptfs_write_inode_size_to_metadata; "
 211                                       "rc = [%d]\n", rc2);
 212                                if (!rc)
 213                                        rc = rc2;
 214                                goto out;
 215                        }
 216                }
 217        }
 218out:
 219        return rc;
 220}
 221
 222/**
 223 * ecryptfs_read_lower
 224 * @data: The read data is stored here by this function
 225 * @offset: Byte offset in the lower file from which to read the data
 226 * @size: Number of bytes to read from @offset of the lower file and
 227 *        store into @data
 228 * @ecryptfs_inode: The eCryptfs inode
 229 *
 230 * Read @size bytes of data at byte offset @offset from the lower
 231 * inode into memory location @data.
 232 *
 233 * Returns bytes read on success; 0 on EOF; less than zero on error
 234 */
 235int ecryptfs_read_lower(char *data, loff_t offset, size_t size,
 236                        struct inode *ecryptfs_inode)
 237{
 238        struct file *lower_file;
 239        mm_segment_t fs_save;
 240        ssize_t rc;
 241
 242        lower_file = ecryptfs_inode_to_private(ecryptfs_inode)->lower_file;
 243        if (!lower_file)
 244                return -EIO;
 245        fs_save = get_fs();
 246        set_fs(get_ds());
 247        rc = vfs_read(lower_file, data, size, &offset);
 248        set_fs(fs_save);
 249        return rc;
 250}
 251
 252/**
 253 * ecryptfs_read_lower_page_segment
 254 * @page_for_ecryptfs: The page into which data for eCryptfs will be
 255 *                     written
 256 * @offset_in_page: Offset in @page_for_ecryptfs from which to start
 257 *                  writing
 258 * @size: The number of bytes to write into @page_for_ecryptfs
 259 * @ecryptfs_inode: The eCryptfs inode
 260 *
 261 * Determines the byte offset in the file for the given page and
 262 * offset within the page, maps the page, and makes the call to read
 263 * the contents of @page_for_ecryptfs from the lower inode.
 264 *
 265 * Returns zero on success; non-zero otherwise
 266 */
 267int ecryptfs_read_lower_page_segment(struct page *page_for_ecryptfs,
 268                                     pgoff_t page_index,
 269                                     size_t offset_in_page, size_t size,
 270                                     struct inode *ecryptfs_inode)
 271{
 272        char *virt;
 273        loff_t offset;
 274        int rc;
 275
 276        offset = ((((loff_t)page_index) << PAGE_CACHE_SHIFT) + offset_in_page);
 277        virt = kmap(page_for_ecryptfs);
 278        rc = ecryptfs_read_lower(virt, offset, size, ecryptfs_inode);
 279        if (rc > 0)
 280                rc = 0;
 281        kunmap(page_for_ecryptfs);
 282        flush_dcache_page(page_for_ecryptfs);
 283        return rc;
 284}
 285
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